The present invention relates to a method for producing a thermoformed part, comprising the steps of:                providing a mould comprising a lower half-mould and an upper half-mould;        providing a heated sheet made of thermoplastic material on said lower half-mould;        coupling said upper half-mould to said lower half-mould in such a manner as to deform said sheet, then cooling it inside the mould until complete consolidation is achieved;        during said cooling, cutting the sheet along at least one edge portion thereof, said cutting operation causing a bending of the edge portion of the sheet against an abutment surface provided on one of said lower and upper half-moulds; and        removing said upper half-mould from the lower half-mould once the consolidation of the deformed sheet has been attained.        
A method of this kind is used, for example, in the production of trim panels for motor vehicle doors. In this field, a sheet of thermoplastic material, combined with a covering if necessary, is heated until the material softens, and is then placed in a thermoforming mould. Thus the mould shapes the sheet, which is cooled and consolidated in contact with the cold walls of the mould. When consolidation is complete, the mould is opened to enable the thermoformed part to be removed.
During cooling in the mould, the sheet can be subjected to a cutting (shearing) operation along at least one of its edge portions, for the purpose of trimming. This cutting operation is normally carried out in such a way that the edge portion of the sheet is bent through a certain angle, less than 90°, until it abuts on an abutment surface provided on the mould.
Depending on requirements, the edge portion may need to be folded, in other words bent back on itself through an angle of more than 90°, the theoretical maximum angle being 180°. This folding operation is conventionally carried out with the mould open, after the forming of the sheet. For this purpose, the edge portion which has been bent during the cutting step in the mould is reheated, so that the bending of this edge portion can be resumed until the desired fold is attained. On a production line, a special station, separate from the thermoforming station, is required for the folding operation.
In view of this, the present invention proposes to provide a method and a mould for producing a thermoformed sheet which can simplify the production process by eliminating the need for a dedicated folding station.